I apologize for the title.. i couldn\'t find a better way to explain the situation.
I use to load properties file using a Property class as described in the URL http
There is no direct way to substitute the property value within the property file/object but you may replace property value once you read via getProperty() method. To produce concatenated messages - have a look at MessageFormat class.
getProperty()
String baseValue=prop.getProperty("url.main");